For example, in a power semiconductor module such as a power conversion module, there may be a problem that the faster switching operation is, the more likely breakdown of a device and noise generation may be caused by overvoltage during turn-off time. The overvoltage during the turn-off time is proportional to a time change rate between inductance inside circuit wiring and current flowing in the power semiconductor module (di/dt).
When a switching time is taken long in order to suppress overvoltage, switching operation becomes slow. Simultaneously, a switching loss represented by time integration of a product of current and voltage is increased. In order to suppress overvoltage and further reduce the switching loss, it is desirable to reduce inductance of the power semiconductor module. There is a method to divide the power semiconductor module into a plurality of circuit units in order to reduce inductance.